The present invention relates to a device for generating ultrasound oscillations, with an ultrasound generator and a resonator connected to the ultrasound generator for conducting ultrasound. The resonator is configured to oscillate longitudinally during operation of the ultrasound generator.
Devices for generating ultrasound oscillations are known and are used, for example, to produce low-frequency high-power ultrasound. Low frequency high-power ultrasound refers to ultrasound with a working frequency of 15 to 100 kHz, preferably 15 to 60 kHz and, for example, 30 kHz and acoustic power above 5 W, preferably 10 W to 1,000 W and, for example, 200 W. For example, piezoelectric or magnetostrictive systems can be used to generate the ultrasound. Low-frequency high-power ultrasound finds ubiquitous applications in the treatment of fluids, such as food, cosmetics, and dyes, as well as nanomaterials. For this purpose, ultrasound having amplitudes of 1 to 350 μm, preferably 5 to 50 μm and for example 15 μm is directly or indirectly transferred via a resonator to the materials to be treated.
In addition to the treatment of materials in open vessels, for example a beaker, a dish or channel-shaped vessel, many applications require low-frequency high-power ultrasound to be introduced into closed vessels, such as reactor vessels or pipes. The closed vessels are often closed at least during treatment with ultrasound. Depending on the application, the closed vessel may be under a lower pressure or a higher pressure than ambient pressure. A lower pressure (vacuum) refers to a pressure between vacuum (0 bar absolute) and ambient pressure (e.g., 1 bar absolute), for example at 0.5 bar. A higher pressure (overpressure) refers to a pressure above the ambient pressure. Some vessels are used with an internal vessel pressure of between 1.5 bar absolute and 1000 bar absolute, for example 3 bar absolute. The material to be treated, for example the liquid, may reside inside the vessel or may flow through this vessel.
For introducing low-frequency high-power ultrasound into such vessel, either the vessel wall can be contacted from outside by the low-frequency high-power ultrasound system to excite oscillations, or a low-frequency high-power ultrasound system can be installed at least partially or completely in the pressurized interior space of the vessel. In particular, the ultrasound generator may be located outside of the vessel and the oscillations may be introduced into the interior space of the vessel via one or more resonators. The ultrasound generator may be an ultrasound transducer and, for example, a linear piezoelectric transducer.
However, in particular when transmitting the ultrasound indirectly into the interior of the vessel through the vessel wall, the ultrasound is transmitted inefficiently by the longitudinally oscillating resonator.
It would therefore be desirable and advantageous to obviate prior art shortcomings and to provide an improved device for generating ultrasound oscillations, with which materials contained in vessels can be more efficiently treated with ultrasound.